RESOLUTION ENHANCEMENT IN OPTICAL LITHOGRAPHY VIA ABSORBANCE-MODULATION ENABLED MULTIPLE EXPOSURES
A method to enhance resolution in optical lithography via absorbance-modulation involves exposing an opaque absorbance modulation layer (AML) to a first waveform having wavelength, 81, with the first exposure forming a first set of transparent regions in the opaque AML and forming a first pattern made of a set of exposed regions in a photoresist layer. Next, the AML is restored to its original opaque state. Next, the restored AML is re-exposed to the first waveform having wavelength, 81, with the exposure forming a second set of transparent regions in the opaque AML and forming a second pattern having a set of exposed regions in a photoresist layer. The first and second patterns in the photoresist layer form a final pattern with enhanced resolution and decreased spatial period than the first pattern. In another scenario, instead of exposing the AML to a first waveform, two waveforms are used (the second being complimentary to the first) to ensure that the transmitted image has sharper edges compared to the original image.
This application is a continuation-in-part of application Ser. No. 11/154,352 titled “System and Method for Contrast Enhanced Zone Plate Array Lithography”, filed Jun. 6, 2005, and application Ser. No. 11/331,752 titled “System and Method for Absorbance Modulation Lithography”, filed Jan. 13, 2005.
BACKGROUND OF THE INVENTION1. Field of Invention
The present invention relates generally to the field of optical lithography. More specifically, the present invention is related to resolution enhancement in optical lithography via absorbance modulation.
2. Discussion of Prior Art
The following references provide general background in the area of optical lithography, but none of them, either by themselves or in combination, teaches or suggests the features of the present invention.
The U.S. patent to Case et al. U.S. Pat. No. 6,879,376 teaches a method and apparatus for exposing photoresists using programmable masks. Case's method increases imaging resolution to provide fully dense integrated circuit patterns made of very small features on photoresist-coated silicon wafers by optical lithography.
The patent publication to Chen et al. (2004/0152011) provides for a reversible photobleachable materials based on nano-sized semiconductor particles and their optical applications, wherein the applications include reversible contrast enhancement layer (R-CEL) in optical lithography, lithography mask inspection and writing and optical storage technologies.
Whatever the precise merits, features, and advantages of the above cited references, none of them achieves or fulfills the purposes of the present invention.
SUMMARY OF THE INVENTIONThe present invention provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) exposing an opaque absorbance modulation layer (AML) to a first waveform having wavelength, 81, the exposure forming a first plurality of transparent regions in the opaque AML and a first pattern comprising a plurality of exposed regions in the photoresist layer; (b) restoring the AML to its original opaque state; (c) exposing the restored AML to the first waveform having wavelength, 81, with the exposure forming a second plurality of transparent regions in the opaque AML and a second pattern comprising a plurality of exposed regions in a photoresist layer, wherein the first and second pattern in the photoresist layer form a final pattern with enhanced resolution and decreased spatial period than the first pattern. It should be noted that more than 2 sequential exposures can be performed in the above-described process. Therefore, the number of sequential exposures should not be used to limit the scope of the present invention.
The present invention also provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) simultaneously exposing an opaque absorbance modulation layer (AML) to a first waveform having wavelength, 81, and a second waveform having wavelength, 82, wherein the second waveform is a complimentary image of the first waveform and the exposure forms a first plurality of transparent regions in the opaque AML and a first pattern comprising a plurality of exposed regions in a photoresist layer; (b) restoring said AML to original opaque state; (c) simultaneously exposing the restored AML to the first waveform having wavelength, 81, and the second waveform having wavelength, 82, with the exposure forming a second plurality of transparent regions in the opaque AML and a second pattern comprising plurality of exposed regions in a photoresist layer, and the first and second pattern in the photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than said first pattern. It should be noted that more than 2 sequential exposures can be performed in the above-described process. Therefore, the number of sequential exposures should not be used to limit the scope of the present invention.
The present invention also provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) projecting an image having wavelength, 81, onto an opaque absorbance modulation layer (AML) formed on top of a photoresist/anti-reflective coating (ARC)/substrate stack, with the exposure forming a first plurality of transparent regions in the opaque AML and a first pattern comprising a plurality of exposed regions in the photoresist layer; (b) restoring the AML to original opaque state; (c) projecting the image having wavelength, 81, onto the restored AML, with the exposure forming a second plurality of transparent regions in the opaque AML and a second pattern comprising a plurality of exposed regions in the photoresist layer, and the first and second pattern in said photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than the first pattern. It should be noted that more than 2 sequential exposures can be performed in the above-described process. Therefore, the number of sequential exposures should not be used to limit the scope of the present invention.
The present invention provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) simultaneously exposing an opaque absorbance modulation layer (AML) formed on top of a photoresist/anti-reflective coating (ARC)/substrate stack to a first image having wavelength, 81, and a second image having wavelength, 82, with 82 being a complimentary image of said 81, and the exposure forming a first plurality of transparent regions in the opaque AML and a first pattern comprising a plurality of exposed regions in the photoresist layer; (b) restoring the AML to its original opaque state; (c) simultaneously exposing the restored AML to the first image having wavelength, 81, and the second image having wavelength, 82, with the exposure forming a second plurality of transparent regions in the opaque AML and a second pattern comprising a plurality of exposed regions in the photoresist layer, and the first and second pattern in the photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than the first pattern. It should be noted that more than 2 sequential exposures can be performed in the above-described process. Therefore, the number of sequential exposures should not be used to limit the scope of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
While this invention is illustrated and described in a preferred embodiment, the invention may be produced in many different configurations. There is depicted in the drawings, and will herein be described in detail, a preferred embodiment of the invention, with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and the associated functional specifications for its construction and is not intended to limit the invention to the embodiment illustrated. Those skilled in the art will envision many other possible variations within the scope of the present invention.
The present invention provides resolution enhancement in optical lithography via absorbance-modulation enabled multiple exposures.
The present invention utilizes absorbance modulation to enable multiple exposures and subsequent resolution enhancement in optical lithography. Two specific embodiments are described, however, the concept can be generalized to any form of optical lithography including (but not limited to) optical projection lithography, contact photolithography, proximity photolithography, scanning image lithography, etc.
In the embodiment, an image is projected, in a first exposure process as shown in
Subsequently, as shown in
After such recovery, a second exposure is performed as shown in
It should be noted that the above process can be iteratively performed for multiple exposures, and the specific number of exposures should not be used to limit the scope of the invention.
Although the illustrations depict a one-dimensional image (i.e., sinusoid), the invention is equally applicable to images in two- and three-dimensions.
According to the first embodiment, the present invention provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) exposing an opaque absorbance modulation layer (AML) 110 to a first waveform having wavelength, 81, the exposure forming a first plurality of transparent regions 109 in the opaque AML 110 and a first pattern comprising a plurality of exposed regions 107 in the photoresist layer (see
Although, the various embodiments detail 2 exposures, it should be noted that more than 2 exposures can be performed, and such exposures are within the scope of the present invention.
Also, according to the first embodiment, the present invention also provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) projecting an image having wavelength, 81, onto an opaque absorbance modulation layer (AML) 110 formed on top of a photoresist 106/anti-reflective coating (ARC) 104/substrate 102 stack, with the exposure forming a first plurality of transparent regions 109 in the opaque AML 110 and a first pattern comprising a plurality of exposed regions 107 in the photoresist layer 106 (see
It should be noted that subsequent exposures can then be conducted in a similar manner, as shown in
It should also be noted that although the patterns shown in the
In the 2nd embodiment, it is important to generate the image at 81 and its complimentary image at 82. This can be achieved by a variety of means including a holographic photomask designed to operate at the two wavelengths. A diffractive or holographic mask may be illuminated by both wavelengths 81 and 82, simultaneously. When the mask is properly designed, this can result in projecting an image at 81 and the complimentary image at 82, coincident with one another. When these images are incident on the AML, a sharpened image is transmitted down into the recording layer (photoresist). Moving the substrate combined with multiple exposures will result in patterns of complex geometries at high resolution and high image quality.
In both embodiments, a thin imaging layer (photoresist) along with additional (transfer) layers may also be used to improve the process robustness (see
According to the second embodiment, the present invention provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) simultaneously exposing an opaque absorbance modulation layer (AML) 302 to a first waveform having wavelength, 81, and a second waveform having wavelength, 82, wherein the second waveform is a complimentary image of the first waveform and the exposure forms a first plurality of transparent regions 304 in the opaque AML 302 and a first pattern comprising a plurality of exposed regions 306 in a photoresist layer 303 (see
Also, according to the second embodiment, the present invention provides for a method to enhance resolution in optical lithography via absorbance-modulation comprising the steps of: (a) simultaneously exposing an opaque absorbance modulation layer (AML) 302 formed on top of a photoresist 303/anti-reflective coating (ARC) 104/substrate 102 stack to a first image having wavelength, 81, and a second image having wavelength, 82, with 82being a complimentary image of said 81, and the exposure forming a first plurality of transparent regions 304 in the opaque AML 302 and a first pattern comprising a plurality of exposed regions 306 in the photoresist layer (see
A system and method has been shown in the above embodiments for the effective implementation of resolution enhancement in optical lithography via absorbance-modulation enabled multiple exposures. While various preferred embodiments have been shown and described, it will be understood that there is no intent to limit the invention by such disclosure, but rather, it is intended to cover all modifications falling within the spirit and scope of the invention, as defined in the appended claims. For example, the present invention should not be limited by the type of waveform used to form the pattern or type of means used to recover AML.
Claims
1. A method to enhance resolution in optical lithography via absorbance-modulation comprising:
- a. exposing an opaque absorbance modulation layer (AML) to a first waveform having wavelength, 81, said exposure forming a first plurality of transparent regions in said opaque AML and a first pattern comprising a plurality of exposed regions in a photoresist layer;
- b. restoring said AML to original opaque state;
- c. exposing said restored AML to said first waveform having wavelength, 81, said exposure forming a second plurality of transparent regions in said opaque AML and a second pattern comprising plurality of exposed regions in a photoresist layer, and
- said first and second pattern in said photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than said first pattern.
2. The method of claim 1, wherein said steps a-c are iteratively performed over multiple exposures with or without relative translation between the projected image and the substrate.
3. The method of claim 1, wherein said restoring step b is done via a uniform exposure to a second waveform with wavelength, 82.
4. The method of claim 1, wherein said restoring step b is done via thermal means.
5. The method of claim 1, wherein said first waveform is a sinusoid.
6. The method of claim 1, wherein said AML, in step a, is simultaneously exposed to a second waveform with wavelength, 82, with said second waveform being a complimentary image of said first waveform.
7. A method to enhance resolution in optical lithography via absorbance-modulation comprising:
- a. simultaneously exposing an opaque absorbance modulation layer (AML) to a first waveform having wavelength, 81, and a second waveform having wavelength, 82, said second waveform being a complimentary image of said first waveform, said exposure forming a first plurality of transparent regions in said opaque AML and a first pattern comprising a plurality of exposed regions in a photoresist layer;
- b. restoring said AML to original opaque state;
- c. simultaneously exposing said restored AML to said first waveform having wavelength, 81, and said second waveform having wavelength, 82, said exposure forming a second plurality of transparent regions in said opaque AML and a second pattern comprising plurality of exposed regions in a photoresist layer, and
- said first and second pattern in said photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than said first pattern.
8. The method of claim 7, wherein said steps a-c are iteratively performed over multiple exposures to first and second waveforms.
9. The method of claim 7, wherein said restoring step b is done via a uniform exposure to said second waveform with wavelength, 82.
10. The method of claim 7, wherein said restoring step b is done via a uniform exposure to a third waveform with wavelength, 83.
11. The method of claim 7, wherein said restoring step b is done via thermal means.
12. The method of claim 7, wherein said first and second waveforms are sinusoidal.
13. The method of claim 7, wherein said first and second waveforms are implemented via a holographic photomask designated to operate at 81 and 82, respectively.
14. The method of claim 7, wherein sharpness and feature sizes of said first and second patterns are controlled by the ratio of the intensities at the two wavelengths, 81 and 82, in addition to photophysical characteristics of the AML.
15. A method to enhance resolution in optical lithography via absorbance-modulation comprising:
- a. projecting an image having wavelength, 81, onto an opaque absorbance modulation layer (AML) formed on top of a photoresist/anti-reflective coating (ARC)/substrate stack, said exposure forming a first plurality of transparent regions in said opaque AML and a first pattern comprising a plurality of exposed regions in said photoresist layer;
- b. restoring said AML to original opaque state;
- c. projecting said image having wavelength, 81, onto said restored AML, said exposure forming a second plurality of transparent regions in said opaque AML and a second pattern comprising plurality of exposed regions in a photoresist layer, and
- said first and second pattern in said photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than said first pattern.
16. The method of claim 15, wherein said steps a-c are iteratively performed over multiple exposures.
17. The method of claim 15, wherein said restoring step b is done via a uniform exposure to a waveform with wavelength, 82.
18. The method of claim 15, wherein said restoring step b is done via thermal means.
19. The method of claim 15, wherein said AML, in step a, is simultaneously exposed to an image having wavelength, 82, that is complimentary to image having wavelength, 81.
20. A method to enhance resolution in optical lithography via absorbance-modulation comprising:
- a. simultaneously exposing an opaque absorbance modulation layer (AML) formed on top of a photoresist/anti-reflective coating (ARC)/substrate stack to a first image having wavelength, 81, and a second image having wavelength, 82, said 82being a complimentary image of said 81, said exposure forming a first plurality of transparent regions in said opaque AML and a first pattern comprising a plurality of exposed regions in said photoresist layer;
- b. restoring said AML to original opaque state;
- c. simultaneously exposing said restored AML to said first image having wavelength, 81, and said second image having wavelength, 82, said exposure forming a second plurality of transparent regions in said opaque AML and a second pattern comprising plurality of exposed regions in said photoresist layer, and
- said first and second pattern in said photoresist layer forming a final pattern with enhanced resolution and decreased spatial period than said first pattern.
21. The method of claim 20, wherein said steps a-c are iteratively performed over multiple exposures to first and second images.
22. The method of claim 20, wherein said restoring step b is done via a uniform exposure to said second image with wavelength, 82.
23. The method of claim 20, wherein said restoring step b is done via a uniform exposure to a third image with wavelength, 83.
24. The method of claim 20, wherein said restoring step b is done via thermal means.
25. The method of claim 20, wherein sharpness and feature sizes of said first and second patterns are controlled by the ratio of the intensities at the two wavelengths, 81 and 82, in addition to photophysical characteristics of the AML.
Type: Application
Filed: Nov 30, 2006
Publication Date: Jul 5, 2007
Patent Grant number: 7989151
Inventor: Rajesh Menon (Cambridge, MA)
Application Number: 11/565,051
International Classification: G03F 7/20 (20060101);